1. Field of the Invention
This invention relates to a method of detecting deviation in position and misshape of transported objects and more particular to a method of detecting those of tip paper which is used for tipping a filter portion of a cigarette in cigarette manufacturing process.
2. Description of the Prior Art
A conventional cigarette with a filter is manufactured in such a manner that a filter plug is positioned between plain cigarettes under the condition that both ends of the filter plug abut an end of the plain cigarettes each, and then a rectangular pieces of tip paper with paste is rolled to envelop the filter plug. Then, after pasting and drying process, the center portion of the filter plug is cut to form a cigarette. The process for rolling the plain cigarette and the filter plug with the piece of tip paper is performed by so-called a filter tip attaching apparatus.
FIG. 12 shows a section for feeding tip paper in a conventional cigarette manufacturing system. The tip paper P is delivered from a tip paper bobbin 10 to a pasting section through delivering rollers 20 and paste is transferred to one side of the tip paper P at the pasting section 30. The tip paper with paste is cut to obtain pieces of paper with a predetermined dimension by a suction roller 40, which rotates at a predetermined velocity, and a knife 50 as illustrated in FIG. 11. Then, the pieces p of tip paper are sucked on a drum face 40a of the suction roller 40 so as to be fed to the transfer drum 60 side with the pasted side of the paper turned up as shown in FIG. 12. The filter plug and the plain cigarette are fed to the transfer drum 60 from an apparatus not shown.
FIG. 10 shows a portion adjacent to the suction roller 40 and the transfer drum 60. On the drum face of the transfer drum 60 are disposed the filter plugs F and supporting members 60a in which inner diameter of a spherical face thereof, which turns outwardly, is the same as the diameter of the plain cigarette at the predetermined intervals in accordance with the intervals of the pieces of tip paper transported. Further, the aligned filter plugs and the plain cigarette are successively transported to the suction roller side while being sucked on the supporting member, the pieces p of tip paper each is stuck to the filter plug with a portion from the tip and around 2 mm to 3 mm therefrom in parallel with the filter plug and the plain cigarette at a portion adjacent to the transfer drum 60 and the suction roller 40. Then, the filter plug and plain cigarette are rolled and stuck together by a heater drum and a rolling hand not shown to produce double filter cigarettes.
However, at an initial stage of the tipping process with the tip paper as described above, the pieces of tip paper are cut into predetermined dimension and are transported on the drum face of the suction drum at certain intervals. Therefore, unless the pieces of the paper are stuck on predetermined portions of both the filter plug and the plain cigarette, the rolling operation at the next stage, in which the filter plug and the plain cigarette are rolled up, may be improper, which causes a defect to be produced.
Therefore, as exemplarily shown in FIG. 9, light projecting and receiving portions 11.sub.A and 11.sub.B of a pair of photoelectric detectors 1.sub.A and 1.sub.B are disposed in the direction vertical to the transporting direction through the suction roller 40, that is, in the direction as indicated by an arrow in the figure, to oppose the dram face 40a. Then, as shown in FIG. 8, the light projecting and receiving portions 11.sub.A and 11.sub.B project a pair of light spots S.sub.A and S.sub.B toward the drum face 40a and then the light reflected from both ends of the pieces p of the transported paper is received. Then, timing of the output signals of the photoelectric detectors 1.sub.A and 1.sub.B based on received light quantity and timing of synchronizing signals are compared with each other to detect the deviation in position and improper cutting of the pieces of the tip paper.
Meanwhile, on the drum face 40a of the suction roller 40 is formed a number of suction holes in rectangular areas which are provided at certain intervals in the direction that the pieces p of tip paper are transported, so that the suction roller 40 sucks the pieces p of tip paper with the suction holes 40b using vacuum force.
In the above structure, the spots S.sub.A and S.sub.B are formed at the same distance from, and slightly inward positions relative to, both ends of the pieces p of tip paper in normal transportation. The reflectivity of the drum face 40a is higher than that of the pieces p of tip paper due to mirror finishing. Nevertheless, the direction of the light projecting and receiving portions 11.sub.A and 11.sub.B are slant relative to a tangent line of the drum face 40a as shown in FIG. 9, consequently the quantity of the light which enters the light projecting and receiving portion 11.sub.A and 11.sub.B increases when pieces p of the paper are positioned at the spots S.sub.A and S.sub.B rather than when the drum face 40a is positioned. Therefore, unless the pieces p of tip paper are slipped in the direction vertical to the transporting direction, tip paper detecting signals are outputted from the photoelectric detectors 1.sub.A and 1.sub.B as indicated in FIG. 7.
Therefore, as exemplarily illustrated in FIG. 6, synchronizing signals a are generated at certain intervals according to the transportation intervals of the suction roller 40, and gating signals g.sub.A and g.sub.B are generated before and after the synchronizing signals a to observe whether or not the rising or falling of tip paper detecting signals e.sub.A and e.sub.B each from the photoelectric detector 1.sub.A and 1.sub.B is detected within the range determined by the gating signals g.sub.A and g.sub.B each, which permits the slipping in position and improper cutting of the pieces of the tip paper to be detected.
With the detecting method described above, although the narrower the width of the gating signals the higher the accuracy for detection, there is a deviation in the interval of the pieces of tip paper due to the mechanical structure including the suction roller, the knife, and a tip paper feeding portion. Therefore, the width of the gating signals should be determined in consideration of certain tolerance.
Therefore, at present, the width of the gating signal is determined according a variety of factors such as adjusting error in a day, daily error, human error, in position of the tip paper, which are calculated from tip paper detecting signals sampled, and error in sensitiveness of the photoelectric detector, which affects the position of the rising and the falling of the tip paper detecting signals.
However, when the width of the gating signals is set as described above, the accuracy for detection becomes poor since such errors are all contained.